Suppose the world had never instituted lockdowns in response to the coronavirus pandemic: There's a strong chance that hundreds of millions more people would have already gotten COVID-19.

That's according to new research from the Global Policy Laboratory at the University of California at Berkeley. In a study published Monday, the lab examined the effects of more than 1,700 coronavirus-prevention measures across six countries: the US, China, South Korea, Italy, France, and Iran.

The restrictions included travel bans, school closings, suspended religious services, event cancellations, and shelter-in-place orders.

Without any limits to people's movement and interaction in the US, they estimated, the number of infections would have nearly doubled every two days from March 3 to April 6. That means about 60 million more people could have been infected. (The US has so far reported 1.9 million cases.)

Lockdowns were even more successful in China, according to the study. The researchers found that policies implemented from January 16 to March 5 in China saved about 285 million people from getting sick. The nation has reported only about 84,000 cases thus far.

China's earliest restrictions were implemented in Wuhan, where the outbreak originated. A March study found that Wuhan's lockdown on January 23 prevented tens of thousands of infections throughout the Hubei province. Without the lockdown, cases in Hubei would have been 65 percent higher, the research estimated.

Lockdown measures also prevented an estimated 54 million infections in Iran, 49 million in Italy, 45 million in France, and 38 million in South Korea, according to the study.

"The deployment of anti-contagion policies in all six countries significantly and substantially slowed the pandemic," the researchers wrote.

But they added that "seemingly small delays in policy deployment likely produced dramatically different health outcomes."

In other words, nations like China benefited from locking down early, while delays in the US and Italy may have resulted in preventable deaths. Indeed, disease modelers from Columbia University recently estimated that the US could have prevented 645,000 infections and 36,000 deaths by locking down one to two weeks earlier.

Europe's lockdowns may have prevented millions of deaths

Lockdowns also were found to have limited coronavirus-related hospitalizations and deaths in Europe. A team of researchers in Italy recently determined that the country's lockdown prevented about 200,000 hospitalizations between February 21 (when Italy's first case was reported) and March 25.

Another study from Imperial College London, published Monday, estimated that lockdown restrictions averted 3.1 million deaths across 11 European countries from the time these measures were implemented in March until May 4.

Italy avoided an estimated 630,000 deaths during that period, according to the study. France, meanwhile, prevented an estimated 690,000 deaths – the most out of the 11 countries.

While less than 1 percent of Germany's population has contracted the virus, the nation averted about 560,000 deaths from March to May, the study estimated. By contrast, Spain and the UK – where more than 5 percent of the population has been infected – were thought to have averted more than 400,000 deaths.

Nordic nations avoided the fewest deaths: an estimated 34,000 in Denmark, 26,000 in Sweden, and 12,000 in Norway. About 3 percent of Sweden's population is infected, compared with 1 percent in Denmark and less than 0.5 percent in Norway.

Overall, the researchers determined that lockdowns had a "large impact on transmission." In all 11 countries, the current reproduction number (the number of other people one sick person infects, on average) was significantly below 1.

That means, on average, a person with COVID-19 passes the virus to just one or fewer people – a sign that an outbreak is contained.

"We cannot say for certain that the current measures will continue to control the epidemic in Europe," the researchers wrote. "However, if current trends continue, there is reason for optimism."

This article was originally published by Business Insider.

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